Flexible matrix for forming a portion of a toothed power transmission belt

ABSTRACT

A method and assembly for making a power transmission belt having driving teeth on opposite surfaces thereof and a tensile member embedded therein. The disclosure also relates to a belt made by the method and apparatus. The method includes providing separate toothed belt portions which will form the two halves of the belt, positioning the first belt portion on a grooved mandrel with the teeth of the first portion disposed within the grooves of the mandrel, applying a tensile member over the outer periphery of the non-toothed surface of the first portion, positioning the other belt portion over the tensile member with its toothed surface facing outwardly of the mandrel; aligning the teeth of the second portion in a predetermined position relative to the teeth of the first portion, retaining the configuration of the teeth of the second portion relative to the teeth of the first portion; and curing the belt portions into a molded integral structure with teeth on opposite surfaces and preferably having a wear-resistant facing covering the opposite toothed surfaces. The disclosed assembly includes means such as a grooved mandrel for maintaining the tooth configuration in the first belt portion and a flexible grooved matrix of special construction for maintaining the tooth configuration in the second belt portion.

This is a division of application Ser. No. 337,056, filed Mar. 1, 1973,now U.S. Pat. No. 3,897,291.

BACKGROUND OF THE INVENTION

This invention relates to a method of making a power transmission belthaving transversely extending driving teeth on opposite surfaces thereofand to an assembly for making such a belt including a flexible matrix ofspecial construction for forming a toothed portion of the belt. Thisinvention also relates to a power transmission belt having driving teethon its opposite surfaces manufactured by the method and assembly andmore particularly this invention relates to such a belt having awear-resistant facing covering the driving teeth on each oppositesurface.

Belts having teeth in opposite surfaces are not new in the art. Forexample, Waugh U.S. Pat. No. 2,699,685 relates to a V-type transverselygrooved power transmission belt having alternating grooves and cogs inopposite surfaces thereof to increase its flexibility in a belt drive.These cogs or teeth, however, do not function to drive the belt so thatthere is no need that the teeth be precisely formed and positioned as isthe case when the teeth serve a driving function as in a timing or geartype belt such as a positive or synchronous drive belt.

Synchronous drive belts having teeth in both driving surfaces also arenot new. It has been customary to mold the driving teeth in one surfaceof such a belt and grind the driving teeth in the opposite surface toachieve an accurate alignment of the teeth in one surface of the belt inrelation to the teeth in the opposite surface. This procedure hasresulted in a generally satisfactory product but has proven to becostly. This procedure also has an additional disadvantage since it isnot practical to provide a wear-resistant facing, for example of arubber impregnated textile fabric material, covering the surface of thebelt to which the driving teeth have been ground or cut.

One problem in making a synchronous drive belt which has teeth molded onits opposite driving surfaces so that a wear-resistant facing can beprovided on both surfaces is that it is extremely difficult to align theteeth of one surface in relation to the teeth of the opposite surfaceand to retain the configuration of the teeth as the belt is beingmanufactured. Adams U.S. Pat. No. 3,673,883 discloses a method ofmanufacturing a power transmission belt having driving teeth in eachsurface with a coating of an elastomeric wear and abrasion-resistantmaterial covering the teeth of each surface. However, this patent doesnot disclose a method of solving the problem of tooth alignment andretention as discussed above.

OBJECTS OF THE INVENTION

It is therefore a primary object of the present invention to provide amethod and assembly for making a power transmission belt having drivingteeth on opposite surfaces of the belt.

It is another primary object of this invention to provide an economicalmethod of producing such a belt having a wear-resistant facing coveringthe teeth in both driving surfaces thereof.

It is another object of the invention to provide a simple and economicalassembly or apparatus for producing such belts.

It is still another important object of the present invention to providea method and assembly for making a power transmission belt havingprecisely aligned driving teeth on opposite surfaces thereof.

It is a still further object of the present invention to provide a powertransmission belt having molded teeth on opposite surfaces thereof witha wear-resistant facing covering the teeth.

It is a more specific object of the present invention to provide aflexible matrix of special construction for the purpose of forming aportion of a toothed transmission belt having teeth on opposite drivingsurfaces.

Other objects and advantages of this invention will become apparenthereinafter as the description thereof proceeds, the novel features,arrangements and combinations being clearly pointed out in thespecification as well as the claims thereunto appended.

It has been found that these foregoing objects are accomplished by amethod of making a power transmission belt having transversely extendingdriving teeth on opposite surfaces thereof and an essentiallyinextensible tensile member embedded therein with the method comprising:(A) providing separate first and second belt portions of flexiblepolymeric material with each portion having a plurality of driving teethon one surface thereof with the teeth extending transversely of theportions; (B) positioning said first portion around a grooved mandrelwith the teeth of the first portion disposed within correspondinglyaligned grooves in the surface of the mandrel and the opposite surfaceof the first portion facing outwardly of the mandrel; (C) applying atensile member around the outer periphery of the opposite surface of thefirst portion; (D) positioning the second portion around the tensilemember with the opposite surface of the second portion in contact withthe tensile member and with the teeth of the second portion facingoutwardly of the mandrel; (E) aligning the teeth of the second portionin a predetermined position relative to the teeth of the first portion;(F) retaining the configuration of the teeth of the second portionrelative to the teeth of the first portion; and (G) curing the first andsecond portions into a molded integral belt structure having teeth onopposite surfaces thereof and the tensile member embedded therein.

It has also been found that the above objects are accomplished by anassembly for manufacturing such a power transmission belt with theassembly comprising (A) first means including grooves for retaining thetooth configuration in the first portion of the belt; (B) second meansincluding grooves for retaining the tooth configuration in the secondportion of the belt; and (C) means for positioning the first portionrelative to the second portion such that the grooves in the first meansare arranged in a predetermined position relative to the grooves in thesecond means.

These objects are also accomplished by a power transmission belt made inaccordance with the method and assembly as described above.

In addition, a specific object of the invention is accomplished byproviding a flexible grooved matrix of integral construction for forminga portion of a toothed power transmission belt with the matrix including(A) a generally cylindrical body of flexible polymeric material; (B)reinforcing means including at least one circumferentially disposedreinforcing member embedded in the body; (C) an inwardly facing surfacehaving a plurality of tooth-forming and retaining grooves disposedtherein with the grooves extending generally axially of the matrix andhaving a plurality of lands alternating therewith; and (D) means at eachaxial end for registering and aligning the matrix grooves with the teethof a toothed belt portion.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a perspective view of a toothed portion of the belt used inthe method and assembly of the present invention;

FIG. 2 is an enlarged sectional view taken on line 2--2 of FIG. 1;

FIG. 3 is a perspective view showing a part of the assembly of theinvention in which two sections of the toothed belt portion of FIG. 1are positioned on a cylindrical mandrel illustrating one step in themethod of the invention;

FIG. 4 is a perspective view of a part of the assembly of the inventionshowing the tension member being applied over the belt sections of FIG.3 illustrating another step in the method of the invention;

FIG. 5 is an enlarged sectional view taken on line 5--5 of FIG. 4illustrating how the belt sections of FIG. 3 are formed into endlessbelt sleeves illustrating another step in the method of the invention;

FIG. 6 is a perspective view of the assembly of the invention showingtwo sections of another toothed belt portion being applied to the beltassembly of FIG. 4 illustrating another step in the method of theinvention;

FIG. 7 is a perspective view showing a pressure roller which is acomponent of the belt assembly of the invention shown in FIG. 6;

FIG. 8 is a side elevational view of FIG. 6;

FIG. 9 is a modification of the invention shown in FIG. 8;

FIG. 10 is an enlarged fragmentary view partly in section of theassembly of the invention illustrating the completion of the steps shownin FIG. 6 and showing how the belt sections of FIG. 6 are formed intoendless belt sleeves by means of the pressure roller of FIG. 7;

FIG. 11 is a perspective view with parts broken away showing a flexiblematrix which is another component of the assembly of the invention;

FIG. 12 is a plan view illustrating another stage in the method of theinvention in which the flexible matrix of FIG. 11 is applied over theassembly shown in FIG. 10;

FIG. 13 is an enlarged sectional view taken on line 13--13 of FIG. 12 tobetter illustrate the construction of the flexible matrix;

FIG. 14 is an enlarged fragmentary view partly in section of thecompleted assembly of the invention illustrating the completion of thestep of the method of the invention shown in FIG. 12;

FIG. 15 is a perspective view of the assembly after cure and removal ofthe matrix illustrating a final step in the method of the invention inwhich the finished belts are cut to size;

FIG. 16 is an enlarged fragmentary perspective view of the finished beltof the invention; and

FIG. 17 is a section taken on line 17--17 of FIG. 16.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the drawings, FIGS. 1 and 2 show a first toothed portion 1 of thebelt formed at least essentially of a flexible polymeric material whichis provided as an initial step in the method of the invention. The beltportion 1 is comprised of a laminated sheet made, for example, of alayer 2 of unvulcanized deformable elastomeric material such as neoprenerubber and a layer 3 of wear-resistant material such as textile fabric.This belt portion 1 will form approximately the bottom or lower one-halfof the completed two-sided gear-type driving belt of the invention. Itis manufactured by forming the laminated sheet in a flat mold or matrix(not shown) in accordance with the method disclosed in Geist et al U.S.Pat. No. 3,250,653, the revelations of which are incorporated byreference herein.

As best shown in FIG. 2, the formed and shaped belt portion 1 includes aplurality of continuous driving teeth 4 extending in a generallyparallel relationship transversely in one surface 5 of the portion. Thedriving teeth 4 have been formed by tooth-forming grooves contained inone surface of the flat mold which have an opposite configuration tothat of the teeth 4. The opposite surface 6 of the portion 1 isgenerally planar or untoothed. The belt portion 1 includes awear-resistant facing 7 which results from the layer 3 being applied tothe surface 5. The facing 7, for example, is composed of rubberimpregnated textile fabric material such as nylon, covering the surfaceof the driving teeth 4. The elastomeric compound which impregnates thefabric layer 3 is preferably compatible with the layer 2 of elastomericmaterial. The fabric facing 7 is applied to the belt portion 1 by themethod described in U.S. Pat. No. 3,250,653. Preferably, in this firststep of the method of the invention the belt portion 1 is preformed butnot cured or vulcanized to any appreciable degree. The components of thelaminated sheet forming the belt portion are joined together by means ofthe pressure applied during the shaping procedure. As will behereinafter described, a second toothed belt portion which will definethe top or upper half of the belt is formed separately in the same or asimilar flat mold or matrix.

As shown in FIG. 3, the toothed belt portion 1 is next wrapped orpositioned around a grooved generally cylindrical mandrel 8 havingaxially extending continuous grooves 9 in its outer peripheral surface10. The mandrel grooves 9 have generally the opposite configuration ofthe teeth 4 of the belt portion 1 so that the teeth 4 are received inthe grooves 9 as the belt portion 1 is positioned around the mandrel 8.The mandrel 8 constitutes a component of the belt assembly 11 of theinvention and is normally constructed of a rigid metal to provide ameans for retaining the tooth configuration in the first belt portion 1with the teeth 4 of the belt portion registering with or lying in thegrooves 9 of the mandrel 8 during all subsequent operations in makingthe belts of the invention.

After the belt portion 1 is wrapped around the surface 10 of the mandrel8, the ends of the portion 1 are spliced to form an endless band orsleeve. The belt sleeve 1 has a width less than the width or axiallength of the mandrel 8 so that the mandrel grooves 9 at the axial endsof the mandrel are exposed for a reason which will hereinafter becomeapparent. It is preferred, as shown in FIG. 3, that the belt portion orsleeve 1 be comprised of two separate toothed belt sections 12 and 12'which are applied one at a time around the mandrel 8 with a space beingallowed between each section 12 and 12' thereby exposing a portion ofthe outer peripheral surface 10 of the mandrel between the sections,also for a reason which will be hereinafter apparent.

The completion of this step of the method of the invention isillustrated in FIGS. 4 and 5. It is preferred that the ends of the beltsleeves 1 be lap spliced as most clearly shown in FIG. 5 at 13. Anadhesive agent such as a neoprene cement may be used to effect tack inthe splice area. It is recommended that a lap splice be used rather thana butt splice since the latter splice might tend to weaken the structureat the splice because the cords in the fabric facing layer 7 would notoverlap. A butt splice would also make it difficult to hold belt sleeve1 together during application of tension member 14 in FIG. 4.

FIG. 4 also illustrates the next step of the invention showing a part ofthe assembly 11 in which the tension layer of the belt is formed byapplying a tensile member 14 around the outer periphery of the oppositesurface 6 of the sections 12 and 12' of the first portion 1 of the belt.The tensile member 14 may be composed of any of the well-knownreinforcing materials well known for that purpose, such as cotton,nylon, rayon, polyester, fiber glass or steel. Preferably, the tensilemember is composed of an essentially inextensible synthetic materialsuch as nylon, polyester, or fiber glass cords or a metal cable. Thetensile member 14 is helically wound around the mandrel over theoutwardly disposed surfaces 6 of the belt sections 12 and 12' bystarting at one axial end of the mandrel 8 and rotating the mandreluntil the tensile member 14 has been wound over the entire surface 10 ofthe mandrel save for the exposed portions previously mentioned. Asuitable adhesive such as a neoprene cement is usually applied duringthis step in the belt making procedure by running the tensile memberthrough an apparatus such as an adhesive applicator (not shown) therebycoating the cord or cable. Alternatively, the adhesive can be applied tothe tensile member by hand using a brush or other suitable means as themandrel rotates. Preferably during this operation the adhesive is alsoapplied to the surface 6 of the sections 12 and 12' to promote adhesionbetween the tensile member 14 and the belt portion 1.

It should be recognized that the method for producing teeth in the firsttoothed belt portion 1 is very similar to the method of producing aconventional synchronous or positive drive belt of the type having teethin only one surface. For instance, the method and apparatus or assemblyof this invention as described in relation to FIGS. 1 through 5 is verysimilar to that disclosed in Geist et al U.S. Pat. No. 3,250,653.

After the tensile member 14 has been wound on the mandrel, a secondtoothed belt portion 15 which has been preformed in the same or asimilar manner as the first toothed belt portion 1 is positioned aroundthe mandrel 8 over the tensile member 14. This is shown in FIG. 6 whichfurther illustrates the assembly 11 of the invention. This portion 15,as was the first portion 1, is comprised of a flexible polymericmaterial such as an unvulcanized deformable elastomeric material. Thesecond toothed belt portion 15 intended to form the upper or top half ofthe completed belt, includes a plurality of continuous driving teeth 16in one surface 17 thereof extending axially of the portion 15 and alsoincludes a wear-resistant facing 18 for example of textile fabricmaterial covering the outer contour of the teeth 16. The teeth 16 of thesecond portion 15 may or may not be of the same configuration as theteeth 4 of the first belt portion 1.

The second belt portion 15 is applied around the mandrel so that thesurface 17 containing the driving teeth 16 faces outwardly of themandrel 8 and the opposite generally planar untoothed surface 19 of theportion 15 is in contact with the tensile member 14. The surface 19 maybe treated with, for example, a solvent wash to increase tack betweenthe tensile member 14 and the portion 15. The ends of the second portion15 are spliced together to form an endless band or sleeve. The sleeve 15has a width less than the axial length of the mandrel 8 so that thegrooves at the axial ends of the mandrel are exposed as was previouslydescribed in relation to belt sleeves 1. It again is preferred that thebelt sleeve 15 be provided in at least two separate belt sections 20 and20'. The belt sections 20 and 20' of the belt sleeve or portion 15 arepositioned over each belt section 12 and 12' of the belt portion 1 sothat each overlying section 20 and 20' of the second portion 15 isaligned with each underlying section 12 and 12' of the first portion 1.The belt sections are of substantially equal width so that a portion ofthe mandrel 8 is exposed both at each axial end of the mandrel andbetween the belt sections.

The second toothed belt portion may be applied by hand around themandrel 8 but it is recommended that means such as a pressure roller 21be used which is associated in some fashion with the mandrel. Thepressure roller 21 best seen in FIG. 7 is made of a rigid metallicmaterial such as steel or aluminum and includes a plurality ofcontinuous grooves 22 disposed in its outer peripheral surface 23extending axially thereof. The roller 21 as shown in FIG. 6 ispositioned generally parallel to and above the surface 10 of the mandrel8 and includes indexing means at each axially opposite end adapted formeshing engagement with the exposed grooves at the axially opposite endsof the mandrel as is most clearly shown in FIG. 8. The indexing meansfor example may be a ring 24 extending radially outwardly from eachaxial end of the roller 21 with the rings 24 including a plurality ofalternating ribs 25 and grooves 26. As the roller 21 rotates about themandrel 8 the ribs 25 of the ring 24 engage the grooves 9 of the mandrel8.

The rings 24 may be made as an integral part of the roller 21 and of thesame type metallic material, or they may be separate flexible endlesselements, for example, constructed of a reinforced vulcanizedelastomeric material. In the latter mentioned construction the rings maybe constituted by an endless toothed transmission belt of an appropriatewidth.

As the top portion 15 of the belt is being positioned around the mandrel8 and over the tensile member 14, the pressure roller 21 exerts pressuredownwardly toward the mandrel thereby forcing or squeezing the beltportions 1 and 15 together causing the assembled belt components toadhere to each other and to the mandrel surface 10. In this way theteeth 16 of the top or upper portion 15 are aligned with the teeth 4 ofthe bottom or lower portion 1.

In a modified assembly as illustrated in FIG. 9, the mandrel 27 itselfmay also include a ring element 28 extending radially outwardly fromeach of its axially opposite ends. The mandrel ring 28 also includes aplurality of alternating ribs 29 and grooves 30 disposed axially of thering 28 with the ribs 25 of the ring 24 of the roller 21 engaging thegrooves 30 of the mandrel ring 28.

FIG. 10 illustrates the completion of the step begun in FIG. 6 after thebelt sections are formed into endless belt sleeves 1 and 15 by means ofthe pressure roller 21 of FIG. 7. Preferably, the top or upper sleeve 15is made endless by means of a butt splice 31 joining the ends of eachbelt section 20 and 20' of the toothed portion 15.

It should be obvious from the method described to this point that theteeth 16 on the top belt portion 15 can be made in any desiredconfiguration and need not be the same configuration as the teeth 4 inthe bottom portion 1. However, for the purpose of illustration, theteeth 16 in the top portion 15 will be of the same configuration (pitch,shape and alignment) as the teeth 4 in the bottom or lower portion 1.

Although it is preferred that the belt components be assembled andvulcanized circumferentially as described in reference to FIGS. 1through 10, it is also possible to vulcanize the toothed belt portionsin a flat condition by using a flat or horizontally disposed mold ormatrix. In the latter event the belt portions could be initially appliedaround a cylindrical mandrel, removed as endless sleeves and then laidup on a flat mold or matrix.

It becomes important at this point in the practice of the method of theinvention to provide means for retaining the tooth configuration of theupper portion 15 as well as maintaining the alignment of these teethrelative to the teeth of the lower belt portion 1. This is accomplishedby providing a grooved means such as a flexible grooved matrix 32 asshown in FIG. 11.

The matrix 32 has a generally cylindrical body formed of a vulcanizedelastomeric material such as natural or synthetic rubber or otherflexible polymeric material and includes outer rows of teeth 33 disposedat each axial end on one inwardly facing surface 35 of the matrix 32with the teeth 34 of each row 33 extending circumferentially of thematrix 32. The surface 35 of the matrix 32 also includes a plurality ofalternating lands 36 and grooves 37 extending generally axially betweenthe outer rows of teeth 33. As shown, the teeth 34 of the outer row 33protrude radially inwardly beyond the surface 35 of the lands 36.Preferably, at least one inner row 38 of teeth 34 is also provided inthe surface 35 of the matrix 32 between the outer rows of teeth 33. Theteeth 34 of the inner row 38 extend circumferentially of the matrixparallel to the teeth 34 of the outer rows 33 and face radially inwardlywith the teeth 34 of the inner row protruding radially inwardly beyondthe surface 35 of the lands 36.

Each individual tooth 34 of row 38 is aligned axially with an individualtooth 34 of row 33 and with a groove 37 extending axially between thetooth 34. The teeth 34 of the matrix 32 act as means for registering andaligning the matrix grooves 37 with the teeth 16 of the tooth beltportion 15 and for that purpose have an opposite configuration to thegrooves 9 of the mandrel 8. The grooves 37 of the matrix 32 serve toform and retain the teeth 16 of the second toothed belt portion 15 withwhich they conform and therefore have an opposite configuration to thatof the teeth 16 of the belt portion 15.

In the part of the assembly 11 shown in FIG. 12, the matrix 32 isapplied around the mandrel 8 and is disposed over the outer belt portion15. The matrix 32 as formed has a greater width or axial length that thebelt portions 1 and 15 so that when the matrix is applied around theouter peripheral surface 17 of the belt portion 15, the protruding teeth34 in the outer rows 33 of the matrix sleeve face inwardly of themandrel 8 and mesh or register with the exposed grooves 9 at the axialends of the mandrel. Similarly, the protruding teeth 34 of the inner row38 of the matrix sleeve 32 mesh with the exposed mandrel grooves 9between and adjacent to the belt sections 12, 12' and 20, 20' of theupper and lower belt portions 1 and 15 respectively. The grooves 37 ofthe matrix sleeve 32 accordingly mesh with the teeth 16 of the secondportion 15 which are aligned therewith.

Preferably as best show in FIGS. 12 and 14, the matrix 32 is comprisedof a plurality of separate matrix segments or strips 39 produced bycutting the matrix sleeve 32 parallel to the tooth forming grooves 37.The segments 39 are disposed in a side-by-side relationship overlyingsubstantially the entire outer peripheral surface 10 of the mandrel 8.The reason for this is that a single cylindrical matrix sleeve isdifficult to position properly around the belt components on themandrel. The separate segments 39 enable any slight errors in dimensionof the matrix 32 to be compensated for during the disposition of thesegments circmferentially around the mandrel 8. Each segment, forexample, may be from about two to about four inches wide and may includefrom about 12 to 15 tooth-forming and retaining grooves 37. As many as15 segments may be disposed about the mandrel on which the nominal beltlength or circumference is approximately 30 inches. Longer belt lengthsgenerally allow use of wider matrix segments.

The preferred internal construction of the matrix 32 is best shown inFIGS. 13 and 14. The body of the matrix has reinforcing means embeddedtherein including two layers 40 and 41 of strain-resisting members suchas cords or cables of textile fabric, fiber glass, or metal which arecircumferentially disposed within the body. Additionally, a plurality ofmetal strips 42, for example, composed of steel are interposed betweenthe layers 40 and 41 of cords or cables. The strips 42 extend generallyaxially of the matrix 32 and are placed radially outwardly of and inradially alignment with the lands 36. The teeth 34 of the matrix 32 maybe comprised of a fiber-loaded elastomeric material to increase theirstiffness or rigidity.

Since the flexible matrix provides means for retaining the toothconfiguration in the second portion and since the teeth of the secondportion when formed must transmit power in the same manner as the teethin the lower portion of the belt, both sides of the belt must be held tosimilar tolerances. Therefore, the construction of the matrix isparticularly critical. The matrix must produce a belt having a toothconfiguration that will repeatedly match that of the pulleys used withthe belt and, consequently, it must maintain precise pitch or spacing ofthe teeth as well as precise alignment of the teeth on the outer surfaceof the completed belt with those on the inner surface of the completedbelt. Furthermore, the matrix must produce near perfect uniformity ofweb thickness between the teeth in order that the finished transmissionbelt function properly on a drive. It is also desirable that the matrixbe capable of repeated use in the method and assembly used to producetransmission belts having driving teeth on opposite surfaces. It hasbeen determined that the construction as described above will bestaccomplish all of these results.

The matrix 32 can be produced in various ways. For example, a matrixpattern (not shown) having an opposite configuration to that of thematrix can be made on a cylindrical mold or mandrel of the type used inproducing regular conventional positive drive belts having teeth in onlyone surface by building a heavier than normal positive drive belt andgrinding teeth on the back side.

An alternate and preferred method is to make the matrix pattern in aflat mold having grooves of the desired configuration and alignment inthe adjacent surfaces of the upper and lower halves of the mold. It hasbeen found that two plies of unvulcanized deformable elastomericmaterial such as neoprene rubber laid up with one ply of square-wovenfabric between the two plies of elastomeric material is suitable for thematrix pattern. This material is placed between the two halves of theflat mold and then the pattern is formed and vulcanized by placing theloaded mold in a heated press.

In the process for making the matrix, the matrix pattern is wrappedaround the cylindrical mold with the ends of the pattern abutting. Twopatterns are required per mold and are spaced in the same manner as beltsections 12 and 12'. The pattern preferably should be coated with a moldrelease agent. Next, a layer of gum stock is wrapped around the mandrelto a suitable thickness, usually approximately 1/16 of an inch, then oneor more plies of reinforcing material in woven or cord form can bewrapped around the pattern. The reinforcing material may include nylonstretch-type fabric or a stable non-stretch or non-shrink type syntheticcord or a metallic cable. If reinforcing members such as steel stripsare to be included in the construction of the matrix, they may be placedon top of the cord or cable after a first layer of reinforcing materialhas been wound around the matrix pattern. In this instance, prior to theapplication of the second cord layer, the strips may be temporarily heldin place by rubber stretch bands. A ply of gum stock may then be appliedon top of the final cord layer and the plied up mandrel placed in asuitable curing apparatus and cured. After cure, the matrix pattern isremoved leaving the matrix. The matrix can then be cut or slit intorelatively narrow strips parallel to the tooth-forming grooves. Anotherpossible method of making the matrix as used in the present invention isto place the matrix pattern on a flat mold and then lay up the gum andfabric components in a flat heated press. However, this method is lessdesirable since the vulcanized matrix sections must fit together to forma cylindrical sleeve and the precise matching of the matrix edges thatabutt on the mandrel under this condition would be extremely difficult.

The completed assembly of the invention is shown in FIG. 14 with thematrix sleeve segments 39 being held in place on the mandrel 8 and onthe first and second toothed portions 1 and 15 by means such as rubberstretch bands 43 or the like.

The assembly 11 of the invention thereby provides means for positioningthe first belt portion 1 relative to the second belt portion 15 suchthat the grooves 9 in the mandrel 8 which provides a first means forretaining the tooth configuration in the first toothed portion 1 of thebelt are arranged in a predetermined position relative to the grooves 37in the flexible matrix 32 which provides a means for retaining theproper tooth configuration in the second portion 15 of the belt.

In the final steps of the invention the entire assembly is placed in asuitable curing apparatus (not shown) and the assembled components arecured into a molded integral belt structure. After curing, the matrix 32is removed from the mandrel 8. The vulcanized belt sleeve structure asshown in FIG. 15 is also removed from the mandrel 8 and placed onto acutting mandrel 44 provided with a rubber cutting surface 45. Here thebelt sleeve is cut into a plurality of toothed belts 47 of integralconstruction having the desired dimensions. The cutting is accomplishedby means of a knife 48 which is common practice in the art.

The belts 47 as shown in FIGS. 16 and 17 include driving teeth 4 and 16on opposite surfaces 5 and 17 and an essentially inextensible tensilemember 14 embedded within the belt with web sections 49 disposed betweeneach aligned pair of teeth 4 and 16 in the opposite driving surfaces 5and 17 of the belt 47. A wear or abrasion-resistant fabric facing 7 and18 surrounds each opposite surface 5 and 17 of the belt 47 covering thedriving teeth 4 and 16 in each surface.

It should be apparent to those skilled in the art that the presentinvention provides a method and assembly for making a power transmissionbelt having driving teeth on opposite surfaces of the belt and a beltincluding a wear-resistant facing covering the teeth in both drivingsurfaces. It should be equally apparent that the present inventionprovides a method and assembly for making a power transmission belthaving precisely aligned driving teeth on opposite surfaces thereof.

While certain repesentative embodiments and details have been shown forthe purpose of illustrating the invention, it will be apparent to thoseskilled in the art that various changes and modifications may be madetherein without departing from the spirit or scope of the invention.

We claim:
 1. A flexible grooved matrix used in combination with a rigidgrooved mandrel for forming and retaining the tooth configuration ofbelt driving teeth of a previously formed toothed belt portion of atoothed power transmission belt, said matrix comprising:A. a generallycylindrical body of flexible polymeric material; B. reinforcing meansincluding at least one circumferentially disposed reinforcing memberembedded in said body; C. an inwardly facing surface having a pluralityof tooth-forming and retaining grooves disposed therein, said groovesextending generally axially of said matrix and having a plurality oflands alternating therewith with said grooves being of an oppositeconfiguration to that of the teeth of the toothed belt portion so as toregister therewith; and D. means at each axial end for registering andaligning said matrix grooves with the teeth of said previously formedtoothed belt portion, said means comprising a plurality of teethdisposed in outer rows at each axial outer end of the matrix extendingcircumferentially thereof with each tooth extending axially thereof onsaid inwardly facing surface, said teeth being of an oppositeconfiguration to that of the grooves of the mandrel so as to registertherewith and protruding radially inwardly beyond the surface of saidlands and said grooves and said lands extending axially between saidouter rows.
 2. The flexible matrix as claimed in claim 1 wherein saidreinforcing means comprises two layers of circumferentially disposedstrain-resisting members and a plurality of rigid elements interposedbetween said member and extending axially of the matrix to providestiffness and rigidity.
 3. The flexible matrix as claimed in claim 1wherein the teeth of said matrix are comprised of a fiber-loadedelastomeric material and said elements are metal strips.
 4. The flexiblematrix as claimed in claim 1 wherein said matrix is comprised of aplurality of separate matrix segments disposed in a side-by-siderelationship held together by a plurality of bands disposed around theouter peripheral surface thereof.
 5. The flexible matrix as claimed inclaim 1 wherein said means for registering and aligning the matrixgrooves with the teeth of a toothed belt portion further comprises atleast one inner row of teeth disposed intermediately of said outer rowswith the teeth in the inner row extending circumferentially of thematrix generally parallel to said outer rows on said inwardly facingsurface and protruding radially inwardly beyond the surface of saidlands and said grooves and said lands extending axially between saidinner and outer rows, said teeth of the inner row being of an oppositeconfiguration to that of the grooves of the mandrel so as to registertherewith.
 6. The flexible matrix as claimed in claim 5 wherein theteeth of said inner row are in axial alignment with the teeth of saidouter rows and said tooth forming and retaining grooves are also inaxial alignment with the teeth of said inner row and said outer rows. 7.In the manufacture of a toothed power transmission belt havingtransversely extending teeth on opposite surfaces thereof, thecombination of:A. a rigid cylindrical mandrel having a plurality ofgrooves in its outer peripheral surface extending axially thereof; B. afirst preformed belt portion of flexible polymeric material having aplurality of driving teeth on one surface thereof, said first beltportion surrounding said mandrel to form an endless belt sleeve with theteeth of said first portion lying within the grooves of the mandrel,said belt sleeve having a width less than the axial length of themandrel so that a portion of the outer peripheral surface of the mandrelat each end is exposed; C. a second preformed belt portion of flexiblepolymeric material having a plurality of driving teeth in one surfacethereof, said second belt portion surrounding said first belt portion toform an endless belt sleeve with the teeth of said second portion facingoutwardly of the mandrel, said belt sleeve having a width less than theaxial length of the mandrel so that a portion of the outer peripheralsurface at each end of the mandrel is exposed; D. a flexible groovedgenerally cylindrical matrix surrounding said second portion, saidmatrix having a plurality of teeth provided in one surface thereof, saidteeth disposed in outer rows at each axial end of the matrix with theteeth of each row extending axially of the matrix and facing inwardly ofthe mandrel, and a plurality of lands and grooves on the inwardly facingsurface thereof extending axially between said rows of teeth, the teethof said matrix having an opposite configuration to that of the groovesof the mandrel and the grooves of the matrix having an oppositeconfiguration to that of the teeth of said second belt portion, saidmatrix having a greater axial length than the first and second beltportions and the teeth of said matrix protrude radially inwardly beyondthe surface of said lands so that the teeth of said matrix face inwardlyof the mandrel and mesh with the grooves of the mandrel in the exposedsurface thereof and the grooves of said matrix mesh with the teeth ofsaid second belt portion.
 8. The combination as claimed in claim 7wherein a tensile member is disposed between said first and second beltportions.
 9. The combination as claimed in claim 7 wherein each saidbelt portion is comprised of two separate belt sections with thesections of each portion being positioned so that each overlying sectionof the second portion is aligned with each underlying section of thefirst portion and with each aligned belt section being of substantiallyequal width so that a portion of the mandrel is exposed between eachsaid belt section.
 10. The combination as claimed in claim 9 whereinsaid matrix includes at least one inner row of teeth disposedintermediately of said outer rows with the teeth of said inner rowextending axially of the matrix and protruding radially inwardly beyondthe surface of said lands inwardly of said mandrel and registering withthe grooves of the exposed mandrel between said belt sections.
 11. Thecombination as claimed in claim 10 wherein the teeth of said inner roware in axial alignment with the teeth of said outer rows and the groovesof the matrix are in axial alignment with the teeth of said inner rowand said outer rows.
 12. The combination as claimed in claim 7 whereinsaid matrix comprises a generally cylindrical body of flexible polymericmaterial and reinforcing means including at least one circumferentiallydisposed reinforcing member embedded in said body.
 13. The combinationas claimed in claim 12 wherein said reinforcing means comprises twolayers of circumferentially disposed strain-resisting members and aplurality of rigid elements interposed between said member and extendingaxially of the matrix to provide stiffness and rigidity.
 14. Thecombination as claimed in claim 12 wherein the teeth of said matrix arecomprised of a fiber-loaded elastomeric material and said elements aremetal strips.
 15. The combination as claimed in claim 7 wherein saidmatrix is comprised of a plurality of separate matrix segments disposedaround said mandrel and said second belt portion with each segmentdisposed in a side-by-side relationship so that substantially the entireouter peripheral surface of said second portion is covered thereby. 16.The combination as claimed in claim 15 wherein said separate matrixsegments are held together by a plurality of bands disposed around theouter peripheral surface thereof.